Two of the biggest problems with passwords is how hard it is to make a secure one and how difficult those are to remember. Solve both problems by using an assortment of commonly misspelled words.
As we (and xkcd) have discussed before, longer, multi-word passwords are harder to crack than short ones with a bunch of random characters in them. Since you’re already in the neighbourhood, you may as well exercise your spelling skills at the same time by choosing hard-to-spell words. This way, you’ll get in the rhythm of typing them correctly. If you’re looking for a few, here’s one of the many lists of commonly misspelled words the internet has to offer.